Multiple sample absorption recording apparatus having a selectively variable cuvetteposition cycle and means to deenergize the recorder between measurement periods



Oct. 3, 1967 w. A. WOOD ETAL 3,344,702

MULTIPLE SAMPLE ABSORPTION RECORDING APPARATUS HAVING A SELECTIVELYVARIABLE CUVETTE POSITION CYCLE AND MEANS TO DEENERGIZE THE RECORDERBETWEEN MEASUREMENT PERIODS 5 Sheets-Sheet 1 Original Filed Sept. '7.1960 025:0: x2520 PCMZU uumaom bro] uumzom :5:

E J 74 v 1967 w. A. WOOD ETAL 3,344,702 MULTIPLE SAMPLE ABSORPTIONRECORDING APPARATUS HAVING A SELECTIVELY VARIABLE CUVETTE POSITION CYCLEAND MEANS TO DEENERGIZE THE RECORDER BETWEEN MEASUREMENT PERIODSOriginal Filed Sept.

3, 1967 w. A. WOOD ETAL 3,344,702

MULTIPLE SAMPLE ABSORPTION RECORDING APPARATUS HAVING A SELECTIVELYVARIABLE CUVETTE POSITION CYCLE' AND MEANS TO DEENERGIZE THE RECORDERBETWEEN MEASUREMENT PERIODS 5 Sheets-Sheet 3 Original Filed Sept. 7,1960 44; I Y 7551 JM/ 06L 1967 w. A. WOOD ETAL 3,344,702

MULTIPLE SAMPLE ABSORPTION RECORDING APPARATUS HAVING A SELECTIVELYVARIABLE CUVETTE POSITION CYCLE AND MEANS TO DEENERGIZE THE RECORDER"BETWEEN MEASUREMENT PERIODS Original Filed Sept. 7. 1960 5 Sheets-Sheet4 I 174 14 2 M0 M6 /.52 M) 1.56? 190 M0 /92 Mil 76 196 I E% 1 PA LINE Yms um I I82 1841 V 7 1 z: Fr R FF- fi= v== 00h 1967 w. A. WOOD 'ETAL3,344,702

MULTIPLE SAMPLE ABSORPTION RECORDING APPARATUS HAVING A SELECTIVELYVARIABLE CUVETTE POSITION CYCLE AND MEANS TO DEENERGIZE THE RECORDERBETWEEN MEASUREMENT PERIODS OriginaLFiled Sept. 7, 1960 5 Sheets-Sheet 52 CO 0 g C U 8 0 Lu 3 1 0: L 3 D: 2 .22 I:

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United States Patent 9 Claims. (CI. 88-14) This application is acontinuation of our co-pending application Ser. No. 54,421, filed Sept.7, 1960, entitled, Optical Density Analytical Apparatus, and nowabandoned.

This invention relates generally to apparatus for use in making physicalmeasurements in the medical, biological and other fields, and moreparticularly is concerned with such apparatus which is used in examiningand analyzing phenomena by means of measuring the absorbance of light ina multiplicity samples of substances being studied.

Many biological, physiological, chemical and interrelated phenomena areanalyzed by passing light through solutions, suspensions and fluids. Thelight is of a constant wave length, which may be changed for differentconditions. Flow rate of blood through the heart can be computed on thebasis of measuring the dilution of tracer materials introduced into theheart through a vein and sampled at a peripheral artery through the useof a densitometer. The concentration of any substance can be measured incases where the concentration is proportional to optical density, bymeasuring the absorbance of light passing through suspensions orsolutions of the substance. Many kinds of reactions, such as enzymecatalyzed reactions can be studied by measuring absorbance.

The usual method of measuring absorbance is to place the solution beingmeasured in a small cell or curvette, as the chamber is called, portionsof opposite walls of which are transparent relative to the wave lengthof the light being used, and to interpose the cuvette between a sourceof the light and a photo-sensitive detecting element. The output of thephotosensitive element is amplified and measured, the meter beingcalibrated in terms of light absorbance or optical density. In recentyears, amplification of the output of the photo-sensitive element haspreferably been accomplished in accordance with a logarithmic functionin order that the meter scale be linear relative to optical density. Theproblem of low intensities of incident light has been solved through theuse of photo-multipliers as the photo-sensitive elements and variouscircuit arrangements have been proposed and used which enableachievement of the linear output desired.

There has been, however, a long-felt need for an apparatus whichutilizes the basic principles of analysis through measurement of lightabsorbance, but which will provide continuous information of kineticreactions occurring over relatively long periods of time, not only for asingle sample, but for a multiplicity of samples, all carried outcoterminously. An important object of the invention is tively andaccurately positioning the cuvettes with respect to the incident beam oflight; and accurately recording the observations of the kineticreactions occurring simultaneously in a multiplicity of samples.

An important object of the invention is to provide a system whichcomprises a source of monochromatic light or a source which is capableof being adjusted or varied for achieving a fine beam of light of anyone of a Wide range of wave lengths or a series of varying wave lengthsfor spectral analysis; a cuvette positioning device by means of which aprogram for discretely interposing one or more of a plurality ofcuvettes can automatically and repetitively becarried out and includingcontrol apparatus for operating the positioning device and pro-settingthe programming there-of; a detecting device, such as a converter whichreceives the beam of light from the source passing through the cuvetteand provides an output signal which is a function of the absorbance ofthe particular wave length of the light by the material contained in thecuvette, it being preferred that the converter include an amplifyingsystem operating on a logarithmic characteristic so that the output islinear with respect to absorbance; and a recording device driven by theoutput of the converter to give a continuous record of the signalreceived from the detecting device.

The achievement of the above mentioned object to a great extent dependsupon an important consideration which it is believed has not beenappreciated until the advent of this invention. When recording kineticreactions, Whether of a single sample or a multiplicity of samples, themovement of the cuvette from position to position results in substantialchanges in the intensity of the light impinging on the photo-sensitiveelement. The information which is sought is hardly enhanced by theinclusion upon the record paper of the spurious responses by therecording instrument of the excursions of its pen for cuvette movementsand conditions which are of no interest. Rather, such recordedinformation is confusing, misleading and often masks the principalinformation sought. The invention herein contemplates a recorderinactivating or immobilizing means which operates in synchronism and incooperation with the cuvette positioning means so that the recording penis not operated unless a measurement is being made. The results of thisarrangement are that the undesired excursions of the recording meterbetween actual desired readings are embodied in straight lines normal tothe direction of movement of the recording paper which can be ignored,while the desired information only occurs as graph lines having at leasta component in the direction of movement of the paper to produce openportions clearly seen and readily measured.

The above arrangement, the accomplishment of which is an importantobject of the invention, enables the graphed information of amultiplicity of coterminously obtained readings readily to be seen uponthe recording paper because of the great contrast between such desiredinformation and the undesired information, because the amplitude of anycurve is a function of the light absorbance and the width of the openportions represents the duration of the respective readings.

An important phase of the invention is the provision of the novelcuvette positioning device whose purpose is accurately and quickly toplace one of a multiplicity of cuvettes in the beam of light and to holdit there for a predetermined length of time. This device operates in conjunction with a novel control circuit which enables the operator tochoose any one or more of the cuvettes to be positioned discretely inthe beam; enables the time of exposure to be adjusted to any desiredvalue; enables any combination of the cuvettes to be exposed insequence, omitting one or more from the sequence; and which ineludes thedisabling means that operates to immobilize the recording device at anytime that there is no motionless cuvette in the light beam.

The mechanical structure of the cuvette positioning device is anoutstanding feature of the invention. In this art, the volume of fluidin the cuvette may be minute and the dimension exposed tothe beam oflight may be ex tremely small'of the order of one millimeter-and thebeam itself may be defined by a pinhole. It is understandable,therefore, that the placement of a multiplicity of cuvettes must beprecise with respect to both position and time. The invention has as afurther object the provision of a novel cuvette positioning mechanismwhich accomplishes the accurate, sequential, and cyclic placement of thecuvettes. This object is accomplished by a novel synchronizingarrangement which temporarily retains the test cuvette in a preciselypredetermined position with respect to the path of thelight beam, whilethe cuvette moving means is disabled.

The accurate positioning of a multiplicity cuvettes in a reliable mannerhas been an unsolved problem heretofore. This invention eliminates allmanners of detents with their wear problems, eliminates the overshoot ofinertiaeffected devices and the indeterminate positioning resulting fromvariations in friction and other causes.

It is not feasible to enumerate the objects of the invention herein,either in terms of the structures which are desired to be constructed inaccordance with the teachings of the invention or in terms of thefunctions, measurements and analyses which can be accomplishedtherewith, but it must be pointed out that these extend far beyond theminimum which have been enumerated above. Complex analyses of manyditferent kinds, never before capable of being recorded in as facile andsimple a manner are now possible with the apparatus herein. For example,it is not known that any apparatus using the technique of measuringlight absorbance has ever been capable of handling a multiplicity ofsamples all at one time, programming them in successive intervals ofcontrolled amounts in order to achieve on a single record, the historyof all of the reactions.

Many uses, techniques, structures and modifications of the system andthe individual parts thereof will occur to those skilled in the art towhich the invention herein appertains, but it is desired to point outthat the nature of the invention is such that it lends itself tosuchflexibility. Because of this, the preferred embodiment as illustrated inthe drawings and described in detail in the specifications is to beconsidered only as one preferred manner in carrying out the invention-anexample, as it were.

In the said drawings, in which the same characters of reference are usedthroughout the several views thereof to designate the same or equivalentelements:

FIG. 1 is a semi-diagrammatic view showing the components of a systemconstructed in accordance with the invention herein.

FIG. 2 is a similar semi-diagrammatic view but utilizing functionalsymbols to designate the various components of the system.

FIG. 3 is a sectional view through the cuvette positioning device withportions shown in elevation.

FIG. 4 is a sectional view through the cuvette positioning device alongthe line 4-4 of FIG. 3 and in the indicated direction.

FIG. 5 is a sectional view through the cuvette positioning device alongthe line 55 of FIG. 3 and in the indicated direction.

FIG. 6 is a fragmentary top elevational view of the cam follower and itsguide means.

FIG. 7 is a fragmentary end-on elevational view of the same.

FIG. 8 is a circuit diagram of the control circuit of the cuvettepositioning device.

FIG. 9 is a plan view of the cam which governs the movement of the camfollower and the cuvette carrier.

FIG. 10 is a reproduction of a typical diagram of the recording made toassay rate and determine specificity of a three reaction enzyme mixtureoccurring simultaneously in different cuvettes.

FIG. 10a is a greatly enlarged reproduction of a portion of therecording diagram of FIG. 10.

A preliminary understanding of the operation of the invention is bestobtained through an examination of FIGS. 1 and 2 of the drawings.

The apparatus of the invention includes a source of monochromatic light20 which is suitably collimated or refracted or in any other opticalmanner narrowed to a fine beam of light such as indicated at 22, passedthrough a suitable iris or slit 24-, and thence through one of thecuvettes shown on the carrier 26. There are four cuvettes, designated28a, 28b, 28c and 28d, each having a different sample of some kindtherein, or a standard sample or the like. The carrier 26 is suitablypositioned by a mechanical moving means designated generally 30 andincluding a follower 37 and cam 34, a connecting link in the form of apush rod 36 mounting the follower, and a motor 38 driving the cam. Themotor is controlled by a suitable control device designated generally 40through electrical connections symbolically designated 41. The controldevice 40 also is arranged to control the operation of an automaticrecording device 42 through a disabling connection which is designated44.

Light emerging from the cuvette under observation at any given timepasses to a photo-sensitive device 46 which is a photo-multiplier in thepreferred embodiment, and thence through an amplifier 48 to the recorder42.

In FIG. 1, the source of light 50 may be of any conventionalconstruction having sufficient quality to provide a good monochromaticlight of suitable beam dimension and having the needed control forspectral analysis. The source 50 may comprise the monochromatic source20, the slit 24, and any refinements that the manufacturer may haveincluded therein.

The control device 40 is shown as a small cabinet which houses relays,switches and the like to accomplish the needed control. The details willbe set forth hereinafter. The means for mechanically moving the cuvettecarrier, the carrier and cuvettes, all are disposed in a suitablehousing such as shown at 52 in FIG. 1 cabled to the other components ofthe system.

Normally the housing 52 with its mechanisms is arranged to be mounteddirectly upon the source 50 at the end thereof from which the beam ofmonochromatic light normally would emerge. This, of course, is tomaintain the distance between the source of light and the cuvette underobservation as short as possible.

The housing 52 also carries on its surface another housing 54 withinwhich the photo-sensitive device 46, and perhaps a portion of theamplifier 48 may be disposed. In any event, at least the photo-sensitivedevice is located in the housing in close proximity to the cuvettethrough which the beam is passing. The signal from the photo-sensitivedevice is transmitted to the amplifier 48 through suitable connections56 and the output of the amplifier is applied to the recorder 42 via achannel 58.

The amplifier 48 is preferably of a construction which provides anoutput that is directly proportional to the absorbance of the substancebeing observed. This is accomplished by having a logarithmiccharacteristic to compensate for the logarithmic character of theabsorbance function. Such circuitry is known and has been in use forsome time.

The recorder is preferably of the self-balancing type with a scale ofrange in which the amplifier 48 normally operates. In a typicalstructure, the recorder has a chart paper which is translated along theX axis at a speed of 12 to 30 inches per hour, and a fast response timeof the order of one second for full scale movement of the pen.

The construction and function of components such as the source 50, therecorder 42 and the amplifier 48 with its photo-sensitive tube 46 aretoo well known to require detailed explanation, although someenlargement upon the nature of these'respective components at this pointmay aid in an understanding and appreciation of the invention as setforth hereinafter.

The conventional source chosen for use herein is required to have asource of monochromatic light, either with or without means for changingthe wave length thereof. The light source is required to be stabilizedby any suitable means, such as regulation circuits and the like.Obviously any suitable monochromatic source of light with such astabilized source can be used, and indeed, the claims appendedhereinafter will make reference to a monochromatic light source.

The recorder 42 is of conventional construction, but the pen movingmeans of the recorder is provided with a connection that can be openedduring movement of the cuvettes so as to effectively immobilize the penduring such movement. The pen of the recorder will therefore execute asubstantially straight line as soon as the next test cuvette is inposition, running from the value of absorbance for the studied substancein one cuvette to the value of absorbance of the substance in the nextcuvette which is seen by the apparatus, whether the same cuvette or adifferent one.

The amplifier 48 and the photo-sensitive device 46 together comprisewhat may be termed an optical density converter. Preferably thephoto-sensitive device is a photomultiplier tube and the amplifierincludes a feedback circuit which keeps the anode current constantregardless of input light level. The output current of the tube providesthe necessary signals which are treated further to render theircharacteristics linear, and this is the output applied by way of thechannel of path 58 to the input circuit of the recorder 42.

The control device 40 and that portion of the cuvette moving mechanism30 which is related thereto are both shown in the circuit diagram ofFIG. 8 to which attention is now invited. Reference may also be had tothe illustration of the housing of the control apparatus shown inFIG. 1. There are several manually operable controls on the housing suchas, for example, six push buttons operating switches and the like. Thisarrangement assumes that there are four positions for cuvettes and thatfour of the buttons are for selecting the cuvettes which will bepositioned in the light beam. The switch buttons which select thecuvettes are designated 60, 62, 64 and 66. The switch button 68 controlsthe operation of a mechanism which continuously recycles the positioningof the cuvettes automatically. These switch buttons are preferablymarked with indicia, 1, 2, 3, 4 and Auto, respectively to give graphicrepresentation to the position control function of each. The switchesare preferably of the self-locking and releasing type, so that thedepressing of one button will :release all of the others which are notalso pressed simultaneously. Thus, if all of the buttons 60, 62, 64 and66 are simultaneously depressed, another push button is needed torelease them. This is the stop button 70, mechanically connected withthe others.

The knob or lever 72 controls the timer mechanism, adjusting its cycleto any desired time at each cuvette position.

'hence the capacitor 80 is connected across the windings 76 and 78 byway of the conductors 82 and 84. The

motor can thus be de-energized and brought to a stop 8 rapidly simply byshort-circuiting the capacitor through a suitable bypass as will bedescribed.

The rotor 74 carries a switch lever 86 which during its rotation,engages the projections 88, 90, 92 and 94 of the switches 89, 91, 93 and95 respectively. The switches each have a pivoted arm 96, 98, 180 and102 to which the projections are respectively secured, the arms beingbiased to engage against the inner contacts 184, 106, 108 and 110 of therespective switches. As the switch lever 86 passes each projection, itswings the arm of that projection to move from its inner contact andengage against its outer contact. Thus, there are four outer contacts112, 114, 116 and 118. The words inner and outer refer merely to theradial positions of the contacts with respect to the axis of rotation ofthe rotor 74 inwardly or outwardly of the arm. The large numerals 1 to 4identify the cuvette controlled by the respective switches.

The outer contacts 112, 114, 116 and 118 connect to respectiveindicating devices, such as gaseous discharge lamps 120, 122, 124 and126 respectively. The lamps, which are preferably small neon bulbs, havea common current return lead 128 that is provided with a seriesballasting resistor 130 and is connected to the power bus 132. Each ofthe arms 96, 98, 180 and 102 is connected to the other side of thesource of power through suitable connections so that as the lever 86rotates, each time it engages an arm, the lamp connected with the outercontact of that arm will ignite. The lamps are suitably identified forthe operator so that the operator knows which of the cuvettes ispositioned in the beam of light.

The arm 96 connects by way of the lead 134 with the line terminal 142through fuse 140. The power line 142- 144 is intended to be aconventional 118 volt, 60 cycle, A.C. line coupled by a suitable prongedplug engaged in an outlet.

The conductor 134 also connects with the conductor 146 that extends tothe connection 148 between the stator windings 76 and 78. The contact104 of the switch 8? connects with the arm 98 of the switch 91; thecontact 186 of the switch 91 connects with the arm 180 of the switch 93;and the contact 188 of the switch 93 connects with the arm 182 of theswitch 95. Each of the inner contacts just mentioned is connected to adifferent one of the push button switches to enable the controlledplacement of the cuvettes.

The push button switches 60, 62, 64, 66 and 68 each have a pair of armswhich are adapted to be moved to either one of two positions. The armsof the switch 60 are 152 and 154; the arms of the switch 62 are 156 and158; the arms of the switch 64 are 160 and 162; and the arms of theswitch 66 are 164 and 166. The Automatic switch 68 has one arm 168. TheOff button 70 is mechanical, as previously stated.

Each of the arms has a contact associated therewith, the upper contactsas viewed in FIG. 8 being normally engaged against the respective armswhen the push-buttons are not depressed while the contacts adjacent thelower arms being open under such circumstances. Depressing any of thepush-buttons will cause the reverse situation to exist, namely, each ofthe upper contacts will become disengaged from its respective arm whileeach lower contact will engage its adjacent arm. The upper contacts areidentified as 170, 172, 174 and 176. There may be an upper arm andcontact on the switch 68 but it is not used. The lower contacts aredesignated 178, 180, 182, 184 and 187. The connecting broken verticallines between the pairs of arms indicate that pairs of arms movesimultaneously upon depression or raising of the particular pushbutton.The connecting slanted broken line between all of the lower armsindicates that any single push-button upon being pressed will releasethe remaining push-buttons and cause them to return to their undepressedcondition, unless the push-buttons are pressed simultaneously. It willbe understood that in the use of the apparatus, the

Z push-buttons marked 1, 2, 3, 4 and Auto may all be depressedsimultaneously and will stay depressed, or any one or more of the firstfour may be depressed alone or with the Auto push-button.

The condition which is illustrated in FIG. 8 is one in which none of thepush-buttons is depressed. Under such circumstances, the jumpers 186,188, 190 and 192 connect all of the upper arms and their contacts inseries with the conductor 194 and the rectifier or diode 196. Thislatter element is for the purpose of converting the alternating currentinto a direct current for operating a DC. relay 198, the solenoid ofwhich is indicated at 208. A storage condenser 282 is connected acrossthe said solenoid, with the return conductor 204 extending to the powerbus 132.

Each of the jumpers is connected with one of the respective arms of theswitches that are adapted to be operated by the motor 38 during rotationof the rotor 74 and lever 86. Thus the jumper 186 is connected by way ofthe lead 134 to the arm 96 as previously stated; the jumper 188 isconnected by the lead 206 to the arm 98; the jumper 190 is connected bythe lead 288 to the arm 100; and the jumper 192 is connected by the lead210 to the arm 102.

The relay 198 controls the operation of three normally closed switches214, 216 and 218. The switch 214 is the timer switch, the switch 216 isthe switch for deactivating the recorder device 42 while the motor ismoving, and the switch 218 has the purpose of causing the rotor 74 ofthe motor 38 to rotate. When the solenoid 200 is energized it separatesthe contacts of all the switches 214, 216 and 218 from their respectiveengaging arms. The contact 220 and its arm 222 of timer switch 214 arein a circuit which extends from the contact 187 of the automatic switch68 by way of the conductor 224 to a timing mechanism 226 and including alead 228 which connects with the lead 134 that extends to the terminal142 comprising one side of the power line.

The circuit just described normally is established across the line 142,144 providing the automatic push-button 68 is depressed and the switch214 is closed. This latter condition obtains unless the solenoid 200 hasbeen energized, and as will be seen, the solenoid in turn is incapableof being energized to achieve this automatic condition unless any one ormore of the cuvette selecting push-buttons 60, 62, 64 and 66 isdepressed. The power bus 132 is con nected to each of the lower contacts178, 180, 182 and 184, and the lower switch arms 154, 158, 162, 166 and168 are all connected to another bus 230 so that the depressing of anyone of these cuvette selecting push-buttons will establish a conditionof conduction between the line terminal 144 and the power bus 132.

T o recapitulate, the timer device 226 will not operate even if theAutomatic push-button 68 is depressed unless at least one of thepush-buttons 60, 62, 64 or 66 is depressed.

The switch 216 closes a circuit by way of a jack 232 to the recorderdevice 42 whenever the solenoid 200 is deenergized. The channel orconducting path is designated 44, as in FIGS. 1 and 2, and extends fromthe contact 234 and the arm 236, which are separated when the solenoid200 is energized. The circuit represented by the path 44 may be andpreferably is in the energization circuit of a motor or other drivingmeans which drives the pen of the recorder device 42. For example, afield winding in a servo drive motor may be opened.

The opening of the switch 218, upon energization of the solenoid 280,separates its arm 240 from its contact 242, thereby removing a shortcircuit through the switch 244 from the capacitor 80. The switch 244 hasan arm 246 normally engaged with a contact 248. If the rotor 74 of themotor 38 is to be rotated, either one of the switches 218 or 244 must beopen. If the switch 218 is open, it is immaterial whether the switch 244is open or not. On the other hand, if the switch 218 is closed and theswitch 244-becomes closed through the operation of the timer 226, thecapacitor 80 will be short circuited and 8 the rotor will stop. Thetimer is adjustable so that the dwell time of the rotor 74, that is thetime which it will remain in non-rotating condition with the lever 86engaged against any one of the projections 88, 90, 92 or 94 iscontrollable through the adjustment of knob 72.

The timer 226 is self-resetting. If the button 68 is depressed, theenergizing of the timer through switch 214 starts the timing cycle,pre-set by the said knob 72. At the end of the preset time, the normallyclosed switch 244 opens and starts the rotation of rotor 74 carryingswitch lever 86 away from that projection upon which it had beenresting. Relay 198 is now energized, opening switches 218 and 214. Thelatter switch causes instantaneous resetting of the timer 226 andclosing of switch 244. Since 218 is open, however, capacitor is notshort-circuited; and the lever arm 86 continues to rotate until itreaches a projection of 88, 9t), 92 or 94 which can, by its engagement,de-energize relay 198 to close switch 218 and stop the motor. Onlyprojections whose push-buttons have been depressed will, uponengagement, result in de-energization of solenoid 280.

By tracing the circuit which has been described above, it will becomeapparent that the lever 86 will not rotate unless any one or more of thepush-buttons 60, 62, 64 or 66 is depressed. If any one of thepush-buttons 60, 62, 64 or 66 is depressed, the only thing that willoccur is that the rotor 74 will rotate the lever 86 to engage the projection of the arm of that switch of the group 89, 91, 93 and 95 associatedwith the circuit of the particular push-button that has been pressed.The condition will remain so long as the operator desires, and withoutchange. In the event that one of the push-buttons 60, 62, 64 or 66 isdepressed along with the Automatic button 68, the rotor 74 will rotateuntil it reaches the particular projection of 88, 90, 92 or 94associated with the circuit of the push-button that has been pressed,will dwell in that position for a length of time controlled by thesetting of the timer mechanism 226, and then will quickly rotate onerevolution and return to the same dwell position associated with thesame sample containing cuvette. This will continue so long as theoperator desires. Likewise, if more than one of the push-buttons 60, 62,64 and 66 is simultaneously depressed, the rotor 74 will rotate, alwaysin the same direction, the lever 86 moving from switch to switch of 89,91, 93 and 95, and stopping only at those switches whose push-button hasbeen depressed, for the length of time controlled by the setting of thetimer mechanism 226. It will be noted that each time the lever 86engages one of the projections 88, 90, 92 or 94, the associated neonlamp 120, 122, 124 or 126 will ignite and remain ignited so long as thelever 86 engages the particular projection.

Another procedure which may be followed using the apparatus, isdepressing more than one of push-buttons 60, 62, 64 and 66 withoutdepressing the automatic pushbutton 68. In this case, the rotor 74 willrotate until the nearest projection is engaged and will remain on thisprojection until the motor 38 is manually energized by some switchmeans, for example, not shown in the drawing. This could be, forexample, a momentary opening switch in the loop which short circuits thecapacitor 80.

In order to demonstrate and trace the circuitry for the conditions whichhave been described above, it will be assumed that the apparatus is inthe condition shown in FIG. 8 with clockwise being the normal directionof rotation of the rotor 74 and its associated lever 86 indicated by thearrow. Assume that the push-button 64 is depressed and permitted toremain in this condition. As soon as the push-button 64 is depressed,contact is established between the arm 162 and the lower contact 182applying power to the bus 132. The upper contact 174- is now separatedfrom the arm 160, and power is applied to the conductor 208 through thearms and contacts to the left of the jumper 190. This establishes aconnection by way of arm 100, contact 188, arm 102, contact 110, lead194, rectifier 196, to energize solenoid 200 and open switches 214, 216and 218. The motor terminal 148 is always connected to one side of theline through lead 134. The power bus 132 connects with the lead 82directly and the stator winding 78, while connecting through thecapacitor 80 and the lead 84 to the other stator winding '76. Underthese circumstances, the rotor 74 will commence rotating in a clockwisedirection. It will be recalled that capacitor 80 is not short-circuitedwhen switch 218 is open.

As the rotor 74 commences to rotate, the lever 86 engages against theprojection 90 and raises the arm 98 from its inner contact 106 to itsouter contact 114; thus, the circuit from the contact 114 through theconductor leading to the lamp 122 back through the ballast resistor 130to the bus 132 is completed. The arm 98 is now in a circuit whichextends by way of the conductor 266 to the jumper 188, therebyestablishing a complete circuit to the lines 142 and 144 for the lamp122, which is labelled 2. The lamp will therefore ignite, indicatingthat the second cuvette position has been reached. It will be noted thatthe terminal 148 is still connected to the line terminal 142 through theconductor 134. The bus 132 is still also connected to the other terminal144 of the line by way of a circuit which is readily traced and hencethe motor 38 continues to be energized and merely passes the projection90 and lights the lamp 2 only momentarily.

Next, the lever 86 engages the projection 92 and raises the arm 108 fromthe contact 108 to the contact 116. The No. 2 lamp 122, in the meantime,has become extinguished. As soon as the circuit is established throughthe lamp 124 from the contact 116 through the arm 100 to the conductor208, the lamp 3 ignites, and will stay ignited so long as the lever 86remains on the projection 92, denoting that the third cuvette positionwas the selected position. With the arm 100 engaging against the contact116, circuit is broken between the conductor 208 and the contact 108.This, it will be recalled, was an essential link to the source of powerfor the solenoid 200 through the rectifier 196 by way of the conductor194, the contact 110 and the arm 102. Removing power from the solenoid200 causes the same to be de-energized and therefore all three of theswitches 214, 216 and 218 are once more closed.

Since the normal condition of the timer 226 is with the switch 244closed, the further closing of the switch 218 will short circuit thecapacitor 80 and the rotor 74 will stop rotating and remain in thatposition until the short circuit is removed. While the solenoid 280 wasenergized, it will be appreciated that the channel 44 leading from thejack 232 to the recording device 42 was open, there by disabling therecorder device 42 and preventing the recording pen from moving. Also,the timer circuit was open and it was not operating since it had notbeen energized by depression of the push-button 68. If the button hadbeen depressed, timer 226 would have commenced cycling when the solenoid200 became de-energized.

The condition described, namely with the lever 86 resting upon theprojection 92 and keeping the arm 100 off the contact 108 will remainuntil the operator changes the condition of the push-buttons. He may dothis by depressing another cuvette positioning button if he so desires,in which case by procedure similarly traced the lever will move throughall of the intervening positions to the new position at which it willremain.

Depressing the Automatic push-button 68 closes the circuit from thecontact 187 through the conductor 244 and through the timer 226 and theswitch 214 as previously explained. When the motor commences rotating,the switch 214 is opened and the timer is reset, but as soon as themotor stops rotating, the timer commences to operate and after a presetinterval it will open the switch 244, thereby enabling the motor oncemore to commence its rotation. As soon as the lever 86 moves 011 of theprojection involved, conditions are established which will keep themotor rotating, including energization of the solenoid 200. If thepush-button of the next projection has been depressed, the lever 86 willstop at that position for a period of time controlled by the setting ofthe timer 226.

It is believed that the above explanation should enable one tounderstand the manner in which it is possible to control rotation of themotor 38, thereby discretely selecting one of a multiplicity ofcuvettes, perform the various functions of disabling the recorder device42 during rotation of the motor, and operate the cuvette positionindicator lamps 120, 122, 124 and 126. In its basic concept, the controlcircuit comprises the switches 89, 91, 93 and in series with solenoid200, each switch being shunted by a push-button switch, 62, 64, 66 and68, respectively. Opening of any one of the normally closed switches 89,91, 33 or 95 by the lever 86 will only be effective to de-energize relay198 if its corresponding normally closed push-button switch has beenopened by manual selection.

Attention is now invited to the mechanism by means of which themultiplicity of cuvettes are moved to the positions desired throughoperation of the motor and its foregoing described switch controls. InFIGS. 3, 4, 5, 6, 7 and 9 the mechanical construction of the cuvettepositioning device 30 is illustrated.

Referring now to FIG. 3, the housing for the cuvette positioningapparatus 52 is shown in sectional view. The housing is formed as anenclosure providing two chambers 300 and 302 separated by a verticalpartition or wall 304. The chamber 300 is that in which the cuvettes28a, 28b, 28c and 28d are adapted to be translated. These cuvettes areof any conventional construction and, as understood, are transparentfront to back as viewed in FIG. 3. They are all mounted on a resilientU-shaped clamping member 306 provided with a hold-down plate 308fastened to a suitable carriage 310 which is mounted upon a pair ofguide rods 312, secured between blocks 314 and 316 located at oppositeends of the chamber 300. The bottom of the chamber 300 is closed off bymeans of a wall 318 which mounts a pin 320. The bottom of the carriage310 mounts an additional pin 322 and there is a helical spring 324stretched between the respective pins 320 and 322 for the purpose ofbiasing the carriage 310 to move to the left as viewed in FIG. 3.

Since the light from the monochromatic source is adapted to be passedthrough one of the cuvettes disposed in the chamber 300 it is essentialthat the chamber 300 be light tight so that stray light does not enterand cause fallacious indications of light absorbance. The right handedge of the chamber 300 is closed off by a wall 326, and the rear andfront sides of the chamber are closed 011 by suitable plates 328 and 330maintained in spaced apart relationship by the blocks 314, 316 andadditional blocks 332 and 333 secured at opposite upper ends of thechamber 3061 by any suitable fastening means, such as those shown in thedrawing and not designated by reference characters. A cover plate 334closes 011 the top of the chamber 300 and is adapted to be removed bymeans of a suitable handle 335. This gives ready access to the chamber300. The chamber 300, as previously stated, is adapted to be secureddirectly over the slit of the monochromatic source such as the source50. In order that the light pass through the chamber, each of the sidewalls 328 and 330 is provided with a aligned opening such as that shownat 336.

The cuvette positioning mechanism provides as many positions of dwell asthe number of cuvettes the clamping member 306 is adapted toaccommodate. Thus in the particular structure which is shown there arefour cuvettes capable of being placed upon the clamping member 306 andthere are four dwell positions achieved in a manner which presently willbe described.

The chamber 302 is defined by a rear wall 338 and a front wall or plate340, and by the partitioning wall 304. A removable U-shaped cover plateis secured around the top, bottom and left hand edges of the chamber 302as viewed in FIG. 3 to define the top, end and bottom walls 340, 342 and344. Any suitable construction may be used, although for convenience thewall 388 and the wall 328 are an integral plate member thus providing aunitary construction to the entire assemblage, and the U- shaped memberforming the walls 340', 342 and 344 has suitable spacing blocks such asshown at 346 secured thereto by bolts or the like. It will be noted thatthe width of the plate 340 is such that it does not reach to thepartitioning wall 304 so that the cover plate 330 overlaps upon aportion of the right hand end of the chamber 302. This is a desirablestructure in order to preserve the light exclusive character of thechamber 300.

Portions of the cuvette positioning mechanism are disposed within thechamber 302 and certain other portions are disposed mounted upon thesurface of the plate 340 exterior of the chamber 302. The portions ofthe mechanism which are mounted on the surface of the plate 340 arecovered by a removable shallow box-like enclosure 350 held in place bysuitable screws with suitable perforations 356 to enable the indicatorlights or lamps 120, 122, 124 and 126 to protrude.

The left hand end of the carriage 310 is secured to a rigid push rod 358by any suitable means such as a pin 360. The push rod extends through anopening 362 provided in the partition wall 304 and the block 314 isnotched at its top in order to permit passage of the said push rod. Atits left hand end, as viewed in FIG. 6, the push rod is provided with ayoke 364 between the bifurcation of which there is mounted a camfollower 366. The cam follower is preferably in the form of a hardenedroller mounted on a shaft 368. On opposite ends of the shaft, as shownin FIG. 7, are preferably provided antifriction guide rollers 370 and372, these rollers being free to rotate independently. Guide ways forthe rollers are provided at 374 and 376, defined by upper and lowertrack members 378 and 379 respectively. In FIG. 7 the upper trackmembers are shown to the left. The track members are secured between theplate 340 and the rear wall 338 by suitable fastening means, such as forexample screws 380 and spacers 382, and may serve as means formaintaining the spacing between the said plate 340 and the wall 338.Obviously the length of the track members 378 and 379 and the guide ways374 and 376 defined thereby must be such as to accommodate the completestroke of the carriage 310 to guide the said movement rectilinearly.

As shown in FIG. 4, the split phase electric motor 38 is mounted to therear of the plate 338 by any suitable means, with its shaft 384protruding into the chamber 302 by way of a suitable opening 386. Aportion of the shaft 384 also extends past the plate 340 for a purposepresently to be described, and there is also an opening 388 in the plate340. A fiat cam 390 of suitable contour, which will be described indetail, is mounted to a hub 392 secured to the shaft 384 by a set screw394 so that rotation of the shaft 384 will result in rotation of the cam390. The follower 366 is adapted to engage against the contoured edge ofthe cam so that rotation of the cam will result in translation of thecuvette carriage 310 right and left as viewed in FIG. 3. A secondbushing or hub 396 is mounted to the end of the shaft 384 by means of aset screw 398 and provides a braking surface for a nylon brake shoe 400mounted to the plate 340 by a screw 402 with its jaws engaged over thehub 396. The hub stud 404 mounts the switch lever 86 by means of a nut406. Obviously, the circumferential locations of the cam 390 and theswitch lever 86 relative to one another are adjustable. The plate 340may be considered a switch plate since it mounts the four switches 89,91, 93 and 95. In the commercial example these switches were in the formof enclosed micro-movement multiple contact switches actuated byrollers, the latter constituting the projections 88, 90, 92 and 94described in connection with FIG. 8.

The lamps 120, 122, 124 and 126 are mounted on a suitable bracket 408which is secured to the switch plate 340. A receptacle for a cable isshown at 410. For convenience, none of the wiring is shown in thedrawings of the mechanical apparatus in order not to confuse the same,although the connections are readily ascertained through an examinationof FIG. 8.

Attention is now invited to FIG. 9, which is a semidiagrammatic viewshowing the manner by which translation of the cuvette carriage 310 isobtained. For the four desired positions of the cuvettes, it isnecessary that the carriage 310 be moved accordingly. If it is assumedthat the opening 336 to be properly aligned with the cuvette 28d, asshown in FIG. 3, under such circumstances the roller 366 would beengaged upon that portion of the cam contour which is designated 412.The cam portion 412 is one of a multiplicity of dwell portions eachdefined by a different radius of curvature. Movement of the cam follower366 along each dwell portion cannot induce rectilinear translation ofthe push rod 358, since the rolling of the cam follower over any dwellportion does not change its position relative to motor axis 384 which isthe pivot point of the cam. Accordingly, precise stoppage of the motor38, such as by complex and expensive mechanical or electromechanicaldetents, is unnecessary. The previously described and relativelyinexpensive dynamic break in combination with the cuvette selectionswitches is more than sufliciently accurate to produce the preciseinterpositioning of each cuvette relative to the openings 336 and thebeam of light passing therethrough.

The next dwell portion of the cam is designated 414 and it is on aradius R The radial distance between R and R represents the distancewhich the carriage 310 must be moved to the right in order that theopening 336 be in perfect alignment with the center of the cuvette 28c.The configuration of the cam edge between the areas 412 and 414 is oflittle consequence so long as the movement of the cuvette carriage isnot so uneven as to produce turbulence in the samples. In the samemanner, dwell areas of the cam along its contoured edge are provided at416 and 418 respectively, with radii R and R corresponding to the thirdand fourth positions of the carriage 310, properly positioning thecuvettes 28b and 28a. It will be appreciated that the carriage 310 willclosely follow the movements of the cam due to the presence of thespring 324 continuously urging the carriage 310 to the left as viewed inFIG. 3.

In this manner, if the cam 390 is accurately made, which is nomechanical problem, the cuvettes 28a, 28b, 28c and 28d will be veryprecisely located relative to the opening 336 for each position of dwellof the cam 390 and its follower 366. Thereby, the cuvettes are capableof being readily aligned with the beam of light coming from themonochromatic source.

If the push-button corresponding to the particular cuvette has beendepressed, the dynamic braking of the motor 38, when lever arm 86engages the projection 92, for example, will stop rotation of cam 390.Due to the circumferential extent of the arcuate dwell portion evenovershoot or stopping short cannot disturb the accuracy of alignment.

As noted in FIG. 1, the housing 54, which carries the photo-sensitivedevice 46, is adapted to be fastened to the front surface of the plate330 in the general location indicated by the broken line outline in FIG.3. It will be thus aligned with the opening 336 and responds to suchlight as passes through the particular cuvette which is located inintercepting position relative to the beam of light from themonochromatic source.

To provide general recapitulation of the operation of the apparatus, foran automatic recording of reactions proceeding in several cuvettes, thetimer control knob 72 is adjusted to the amount of dwell it is desiredoccur when each of the pertinent cuvettes is located in the beam of 13light, and the buttons 60, 62, 64 and 66 corresponding to the cuvettestogether with the Automatic push-button 68 are depressed. The motor willdrive the cam to position each of the cuvettes in alignment with thebeam for the time which has been set on the timer 226. Between dwellpositions of the cam 390 and its follower 366, the recorder 42 will bedisabled and the pen will not move. Each time that a cuvette ispositioned in the front of the opening 336, the indicator light 120,122, 124 or 126 corresponding to that cuvette will be lighted and willremain lighted so long as the cuvette is in the particular position.When it is desired that the recording cease, the

operator depresses the stop button 7 In order further to illustrate themanner in which the apparatus is used for making a record ofmultiplicity reactions occurring simultaneously in multiplicitydifferent cuvettes, the resulting recording sheet with interpretiveinformation is shown in FIGS. and 10a. There is illustrated a section ofthe recording paper taken from an actual run in which the paper movesrelatively to the left and a recording therefore starts at the left andproceeds continuously to the right. Four cuvettes were used in thiscase, one of which served as a standard and had either an undilutedsample, or water, or was simply blank. The others had reactionsoccurring of a related nature, such as for example of enzyme alone, withdifferent proportions of added reagents or different added reagents. Asnoted, the scale at the left comprises the absorbance as recorded by therecorder 42 and the bottom scale is a time scale with the distancebetween vertical lines as indicated cor-responding to the time intervalset by the adjustment 72 of the timer 226. The absorbance scale can -beadjusted to any given value by scale factor controls inherent in theconstruction of the amplifier 48. Usually the range over which thisexperiment is to be conducted 'is fairly well known and hence the numberof units of this range is chosen to be substantially the full scaleexcursion of the recorder pen. As readily seen from FIGS. 10 and 10a,four distinctly labeled curves have been coterminously plotted. Of eachset of four adjacent, generally horizontal, plots, the lowest, shown as420 in FIG. 10a and Standard in FIG. 10, represents the absorbance ofthe contents of the standard or blank cuvette, such as the cuvette 28d.The other reaction curves A, B, and C in FIG. 10 comprise respectivelyrepeated progressive plots of the graph segments 424, 428, and 432 shownin FIG.

10a. Each discrete, generally horizontal segment 420, 424, 428, and 432denotes the relative absorbance of the contents of its associatedcuvette during the relatively short period of time that that cuvette isimmobilized in a precise position between the light source 26 and theph0 tosensitive device 46, as illustrated in FIG. 2. This may representa time of two and one-half to sixty seconds. After the completion of therecording as determined by the timer 226, the cam rotates very quicklyto its next position. During this movement, the recording pen stops anymovement. The approximate time between dwell positions of the cam is oneand one-half seconds with a motor that rotates at approximately 10 rpm.

As previously described, during the short intervals that the switch 218is opened and motor 38 drives the cam 390 for repositioning the cuvettecarriage, the switch 216 also is opened. When the next test position ofthe cuvette carriage is reached, the motor is de-energized, the switch216 closes, the recorder is once more energized, the pen immediatelymoves along the path 422 to the next posi- -tion very quickly, andcommences to record the changes occurring in second cuvette 28c at thelevel 424. Subsequent to the precise sequential positionings of thecuvettes 28c, 28b, and 28a, the pen moves along the path 426 to thethird position 428, records, moves along the path 430 to the lastposition 432, records and then once more returns along the line 434 tograph the absorbance of the contents in the sample cuvette 28d, whichideally 7 would be a horizontal extension of the segment 420. This '14continues throughout the entire run with the result of formation of therecording which is shown in FIG. 10.

It is believed that the invention has been sufficiently explainedwithout any further detail such as to enable those skilled in this artto understand the complete operation thereof. It is desired to point outthat considerable variation is capable of being made without in any waydeparting from the spirit or scope of the invention as defined in claimsappended hereinafter.

What it is desired to be secured by Letters Patent in the United Statesis:

1. Apparatus for the programmed selection of a multiplicity of cuvettesand for recording coterminously the measurement of the absorptioncharacteristic of a sample disposed in each selected cuvette as afunction of time upon a single recording surface, which comprises:

(a) means for generating a beam of radiant energy;

(b) means for transporting the cuvettes into the path of the beam, saidtransporting means comprising:

(i) a rack for supporting the cuvettes;

(ii) means for supporting the rack in the path of the beam and forallowing movement of the rack along a path transverse to the axis of thebeam;

(iii) a motor driven cam having at least as many lobes of differentradii as the number of cuvettes which the rack can support; and

(iv) cam follower means for moving the rack along the supporting means;

(0) control means for programming the operation of the transportingmeans for repetitive cycles of movement during which selected cuvettesare held in a measurement position in the path of the beam for apredetermined measurement period;

(d) transducer means for generating an output signal having a parameterwhich is a function of the amount of beam energy absorbed by a sample ina selected cuvette; and

(e) means for recording coterminously the magnitude of the parameter ofthe output signal which is a function of the amount of beam energyabsorbed by a sample in a selected cuvette for each selected cuvetteupon a single recording surface solely as a function of time.

2. Apparatus for recording continuously the light absorbance of aplurality of samples disposed respectively in separate cuvettes, some ofwhich may be selected, which comprises: a source of light and meansforming a beam of said light, a cuvette positioning device havingcuvettes arranged for sequential disposition thereof intercepting thebeam, electric circuit pre-settable control means programming theoperation of the positioning device for repetitive cycles of selectedcuvettes in said disposition for a predetermined measuring period, menasfor converting the light passing through a cuvette into an out putsignal the character of which is related to the absorbance in thecuvette and including photo-sensitive means arranged in the beam at aposition to receive light that has passed through said cuvette, andrecording means adapted to record the relative amplitudes of theabsorbance output signals during the measuring periods of the selectedcuvettes solely as a function of time upon a single recording surface,said recording means comprising marking means movable in a firstdirection in response to output signals and a recording surface forreceiving marks applied by the marking means, said recording surfacemoving with respect to said marking means in a second directiontransverse to said first direction, wherein said control means has meansfor stopping the movement of the marking means upon the recordingsurface in said first direction at such times as the cuvettes are beingmoved between their respective positions and wherein said recorderregisters an indication of relative signal amplitude only when a cuvetteis in proper intercepting disposition.

cuvettes in paths which repeatedly dispose the cuvettes sequentially inthe beam and hold each selected cuvette in said beam for a predeterminedtime, means arranged -to receive the beam after passing through thecuvettes when so disposed andto convert same into an electric signal thecharacter of which is related to the absorbance of the sample inwhichever selected cuvette is in the beam at the time, recorder meanscomprising a movable marking member and a recording surface movable withrespect to said member in a direction transverse to the movement of saidmember, and the electric signal being applied to the recorder means toobtain a recording, first electrical circuit means adapted toactivatesaid recorder means so as to cause said marking member to placean indication of absorbance signal amplitude upon said recordingsurface, a second electric circuit for energizing said transportingmeans, and relay means for rendering the first circuit inoperative whenthe second circuit is operative, said transporting means comprising anelectric motor, the first circuit means including a normally closedswitch and the second electrical circuit comprising a shunting loopconnected in parallel with an energizing winding of said motor todeactivate same when said loop is closed, and said relay means operableto open both of said first and second circuits simultaneously to operatethe motor and deactivate said recorder means.

tric motor, a control apparatus for said motor, and a recordinginstrument adapted to receive signals from said signal producing meansrelated to absorbance, said control apparatus including anelectromagnetically energized three circuit switch device, one circuitcontrolling the operation of said recording instrument, one circuitcontrolling the energization of said motor, and one circuit controllingthe re-cycling of motion of said cuvettes, and manual means forselectively pre-setting the control apparatus to perform the functionsof energizing the motor while the recording instrument is de-energizedand vise verse, and energizing the re-cycling circuit to energize themotor a predetermined time after said motor has been stopped at anyposition.

5. Apparatus as recited in claim 1 wherein said cam follower means ismounted with respect to said cam to be reciprocated thereby and saidtransverse path is rectilinear, the movement of said cam follower meansand said rack being interrupted both during absence of drive by saidmotor and during coaction of said cam follower means with each of saidlobes.

6. Apparatus for recording coterminously the light absorbance of amultiplicity of samples disposed respectively in separate cuvettes, someof which may be selected, which comprises: a source of light and meansforming a beam of said light, a movable cuvette carrier having holdermeans for a multiplicity of cuvettes; a cuvette positioning devicedrivingly coupled with said carrier to move it in a path which disposesthe carrier in a multiplicity of positions relative to the beam, suchthat each cuvette mounted on said carrier sequentially intercepts thebeam; electric circuit pre-settable control means programming theoperation of the positioning device to produce repetitive cycles ofselected cuvettes in said beam-intercepting positions for apredetermined measuring period; means converting the light passingthrough a cuvette, when in its beam-intercepting position, into anoutput signal the character of which is related to the absorbance in thecuvette and including photo-sensitive means arranged in the beam ata'position to receive light that has passed through said cuvette; andrecording means which coterminously records the relative amplitudes ofthe absorbance output signals of all selected cuvettes during themeasuring periods of the said selected cuvettes, solely as a function oftime, upon a single recording surface; said recording means comprisingmarking means movable in a first direction in response to saidabsorbance output signals, means applying the said absorbance signals tosaid marking means to cause said movement thereof in said one directionin an amount proportional to absorbance, and a recording surfacereceiving marks applied by the marking means, said recording surfacemoving with respect to said marking means in a second directiontransverse to said first direction, said control means having meansinhibiting the absorbance output signals from being applied by saidapplying means to said marking means while said cuvettes are being movedbetween their respective beam-intercepting positions to prevent themovement of the marking means in said first direction at such times asthe cuvette carrier is being moved.

7. Apparatus as claimed in claim 6 in which said means inhibiting saidabsorbance output signals prevents all movement of said marking meansduring the times the cuvette carrier is being moved.

8. Apparatus for the programmed selection of a multiplicity of cuvettesand for recording coterminously the measurement of the absorptioncharacteristic of a sample disposed in each selected cuvette as afunction of time upon a single recording surface, which comprises:

(a) means for generating a beam of radiant energy;

(b) means for transporting the cuvettes into the path of the beam;

(c) control means for programming the operation of the transportingmeans for repetitive cycles of movement during which selected cuvettesare held in a measurement position in the path of the beam for apredetermined measurement period, said control means comprising:

(i) means for selecting each of the cuvettes containing a sample to bemeasured;

(ii) means for stopping the transporting means when a selected cuvetteis properly disposed in the beam path for measurement;

(iii) means for adjusting the length of the measurement period; and

(iv) means for starting the transporting means at the end of themeasurement period;

(d) transducer means for generating an output signal having a parameterwhich is a function of the amount of beam energy absorbed by a sample ina selected cuvette; and

(e) means for recording coterminously the magnitude of the parameter ofthe output signal which is a function of the amount of beam energyabsorbed by a sample in a selected cuvette for each selected cuvetteupon a single recording surface solely as .a function of time, saidmeans for recording including marking means having motion relative tosaid recording surface in response to said output signal when a selectedcuvette is properly disposed in the beam path for measurement, saidcontrol means and said means for recording being intercoupled forexerting disabling control upon said means for recording during theperiods of time that the transporting means is transporting saidcuvettes, such that during said time periods said marking means isprevented from being responsive to said output signal.

9. Apparatus for the programmed selection of a multiplicity of cuvettesand for recording coterminously the measurement of the absorptioncharacteristicof a sample disposed in each selected cuvette as afunction of time upon a single recording surface, which comprises:

(a) means for generating a beam of radiant energy;

(b) means for transporting the cuvettes into the path of the beam;

(0) control means for programming the operation of the transportingmeans for repetitive cycles of movement during which selected cuvettesare held in a measurement position in the path of the beam for apredetermined measurement period;

(d) transducer means for generating an output signal having a parameterwhich is a function of the amount of beam energy absorbed by a sample ina selected cuvette;

(e) means for recording coterminously the magnitude of the parameter ofthe output signal which is a function of the amount of beam energyabsorbed by a sample in a selected cuvette for each selected cuvetteupon a single recording surface solely as a function of time, saidrecording means comprising:

(i) marking means movable along a locus in response to output signalsreceived from the transducer means;

(ii) a recording surface, for receiving marks applied by the markingmeans; and (iii) means for causing the relative movement of therecording surface and the marking means in a direction transverse to themarking means locus; (f) means for generating a signal indicating that aselected cuvette is in said measurement position; and (g) means enablingthe movement of the marking means along said locus upon receipt of suchmeasurement position signal and inhibiting that movement in the absenceof such signal.

References Cited UNITED STATES PATENTS 2,675,734 4/1954 Hasler et a1.88-14 2,984,146 5/1961 KWart et al. 8814 3,026,764 3/1962 Allen et a1.88-44 JEWELL H. PEDERSEN, Primary Examiner. DAVID H. RUBIN, Examiner.

R. J. STERN, Assistant Examiner.

2. APPARATUS FOR RECORDING CONTINUOUSLY THE LIGHT ABSORBANCE OF APLURALITY OF SAMPLES DISPOSED RESPECTIVELY IN SEPARATE CUVETTES, SOME OFWHICH MAY BE SELECTED, WHICH COMPRISES: A SOURCE OF LIGHT AND MEANSFORMING A BEAM OF SAID LIGHT, A CUVETTE POSITIONING DEVICE HAVINGCUVETTES ARRANGED FOR SEQUENTIAL DISPOSITION THEREOF INTERCEPTING THEBEAM, ELECTRIC CIRCUIT PRE-SETTABLE CONTROL MEANS PROGRAMMING THEOPERATION OF THE POSITIONING DEVICE FOR REPETITIVE CYCLES OF SELECTEDCUVETTES IN SAID DISPOSITION FOR A PREDETERMINED MEASURING PERIOD, MEANSFOR CONVERTING THE LIGHT PASSING THROUGH A CUVETTE INTO AN OUTPUT SIGNALTHE CHARACTER OF WHICH IS RELATED TO THE ABSORBANCE IN THE CUVETTE ANDINCLUDING PHOTO-SENSITIVE MEANS ARRANGED IN THE BEAM AT A POSITION TORECEIVE LIGHT THAT HAS PASSED THROUGH SAID CUVETTE, AND RECORDING MEANSADAPTED TO RECORD THE RELATIVE AMPLITUDES OF THE ABSORBANCE OUTPUTSIGNALS DURING THE MEASURING PERIODS OF THE SELECTED CUVETTES SOLELY ASA FUNCTION OF TIME UPON A SINGLE RECORDING SURFACE, SAID RECORDING MEANSCOMPRISING MARKING MEANS MOVABLE IN A FIRST DIRECTION IN RESPONSE TOOUTPUT SIGNALS AND A RECORDING SURFACE FOR RECEIVING MARKS